Right now, the explosive courtroom drama in kansas where that sheriff's deputy took the stand to defend himself against charges he murdered his wife and then set their home on fire to cover up the crime. He claims she was depressed and took her own life. Abc's gio benitez is here with all those details for us, good morning, gio. Reporter: The prosecution argues brett seacat killed his wife two days after she handed him divorce papers. Now, at the center of this murder trial is what prosecutors call his odd behavior the day before his wife's death. This is the fiery home where vashti seacat died from a gunshot wound to the neck inside the burning house. A day before they saw him destroying hard drives and asking for a projector. Prosecutors found his old cell phones in the trash of his kansas office. Why did you melt the two hard drives as opposed to just tossing them in the trash? If you leave a hard drive in a trash, most identity thieves would not have any problem at all accessing that hard drive in some form or another. Reporter: The prosecution is arguing that he used a projector to forge his wife's suicide note, but the former police officer says he was using it for a fraud investigation. I was showing how a false social security card was made. I was going through the steps that I had been told about to see if they were actually applicable. Reporter: As for those discarded old cell phones, the 37-year-old says he was looking to protect his identity. Websites that said don't sell your old cell phone, said destroy them. Reporter: He argues his wife killed herself following depression he says was caused by a weight loss supplement called hcg. Do you know whether or not your sister was using that diet supplement? Yes. Reporter: But in court her friends testified that she did not seem depressed and was optimistic about starting a life away from brett seacat. In an interview with abc news her family says the young mother who filed for divorce two weeks before her death never wanted to hurt brett with those divorce papers. She was sad. She was hurting someone. She was sad that she would hurt anyone. As we all would even when I had a breakout, I'm sad for that person and I'm sad I'm having to hurt them. Reporter: Also at issue, the evidence. While prosecutors argue brett's pants had gasoline on them, yesterday a forensic expert testified that they were not properly sealed in the right kind of evidence bag, robin. Okay, gio. We'll bring in "gma" legal analyst dan abrams with pore on this. Were you surprised he took the stand at all? I'm always surprised when a defendant in this kind of case takes the stand but he's in a tough spot. It's not just because there's a lot of evidence against him. It's because it's the type of evidence that they have against him. Meaning it's the type of evidence that jurors can understand and relate to which is things that he said that were incriminating, things that he did that were incriminating. Why didn't he do other things? I mean, the note that was found in his pocket, this isn't dna and complicated stuff. Had did just sort of stuff that comes from the gut that makes you say, well, wait a second, what else could be the explanationy that's why I think he's taking the stand is to try to offer up other explanations. He did seem to have an answer to everything and did seem like he was trying to explain away anything that could give the impression that it was premeditated. That's right. I mean, look, the problem is while all of his answers make total sense, right, hard drive, want to get rid of it because you don't want identity thieves. Don't want to just leave your cell phones around, discard old cell phones, et cetera, the problem is this all happened right before his wife dies. You put that in conjunction with the other evidence in this case, that's the problem he's got. It's not just one isolated piece of evidence, it's all of the evidence together. He's back on the stand and going to face tougher questions today. Right, the cross-examination is going to be the key. Can he hold up, does his story stick together? All rign, thanks so much. Have a great week.

This transcript has been automatically generated and may not be 100% accurate.

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